1. Field of the Invention
The present invention relates to semiconductor substrate processing equipment. More particularly, the present invention relates to an improved shield assembly for a vacuum deposition chamber.
2. Description of the Background Art
Semiconductor devices are created by depositing thin layers of metal upon a substrate or wafer. The materials are deposited in predefined configurations and layers to give the device its required electrical properties. Suitable deposited materials include aluminum, titanium, gold, copper, silicon, and/or various metal alloys. The substrate upon which these materials are deposited is typically formed from a semiconductor material.
The deposited material originates from a target located over the substrate being processed. Various techniques are employed in causing the target material to deposit on the underlying substrate. These processes include sputtering and physical vapor deposition (PVD). In each instance a deposition environment is created within a vacuum chamber overlying the substrate.
For example, in PVD the vacuum chamber is filled with a gas such as argon. Thereafter, a negative voltage is applied to the target, with the chamber remaining grounded. The voltage excites the argon gas and transforms it into a plasma state. The plasma state, in turn, results in argon ions bombarding the target and sputtering material therefrom. As a result, a fine layer of target material is deposited upon the underlying substrate.
In all known PVD processes the target material has a tendency to scatter and deposit on surfaces other than the substrate. Over time, the scattered materials accumulate. This build-up can interfere with the normal operation of the chamber. For example, accumulated materials have a tendency to flake off over time and land upon the underlying substrate. This causes defects in the resulting semiconductor devices.
One way to overcome the problems associated with scatter is to periodically clean the interior of the deposition chamber. This can be accomplished through etching or mechanical abrasion techniques. That is, the deposition process is stopped, and the chamber is opened to permit a user to remove scattered deposits via chemicals or with the aid of tools. However, both etching and abrasion result in a premature wearing of the surfaces within the vacuum chamber, which leads to untimely replacement of the chamber.
An alternative to cleaning the chamber is to shield the internal components of the chamber with a disposable lining. This is advantageous in that once a build up of scattered materials collects upon the shield, it can be removed and replaced. This solution is desirable because it avoids any scattered materials from depositing on non-removable areas within the chamber. It also avoids the use of damaging abrasion or etching techniques.
One existing shielding arrangement is illustrated in FIGS. 1 and 2. FIG. 1 is an exploded view of the shield assembly as it is positioned within a vacuum deposition chamber. The assembly includes an adapter plate, a collimator, a lower shield component and a multi-part upper shield assembly. Screws are employed in securing both the lower shield and the multi-component upper shield assembly to the adapter plate. Once secured the shield assembly protects the adapter plate and other components of the chamber against the collection of scattered materials.
Yet, this shield assembly can only be replaced by removing the entire adapter plate (with the shield components attached thereto) from the deposition chamber. Once removed the various shield components are uncoupled from the adapter. Specifically, the lower shield component, and the various pieces of the upper shield component, are unscrewed from the adapter plate. Thereafter, new shield components are secured to the adapter plate. The adapter plate is then secured back within the deposition chamber.
Although the above described shield assembly is effective in preventing the accumulation of scattered materials, it suffers from the drawback of complexity. For example, both the upper and lower shields require multiple interconnections with the adapter. As such, replacement of the shield can only be accomplished by removing the entire adapter plate from the chamber. This requires an extended period of time during which no manufacturing processes are undertaken and the chamber is open to impurities within the atmosphere.
Therefore, there exists a need in the art for an improved shielding assembly which can be easily and quickly removed and replaced from a deposition chamber.
It is therefore one of the objectives of this invention to enable the quick and easy removal and installation of a shield assembly within a vacuum deposition chamber.
It is also an object of this invention to secure a shield assembly to an adapter plate with a minimal number of parts and/or fasteners.
Still another object of this invention is to prevent the accumulation of scattered materials upon the deposition chamber by way of a shielding arrangement.
These and other objectives are carried out by an improved shield assembly for a substrate processing chamber. The assembly includes an adapter plate that functions to support a target assembly. The plate has a central opening defined by a first cylindrical extent of a first diameter and a second cylindrical extent of a second reduced diameter. The adapter has both upper and lower peripheral edges, with a pair of opposed locking apertures formed within the upper peripheral edge.
The assembly also includes an upper shield component defined by upper and lower peripheral edges. A series of threaded apertures are formed within a lower peripheral edge of the shield, and a pair of opposed flanges are integrally formed upon the upper peripheral edge. Each of the flanges has a locking aperture formed therein. The upper shield additionally includes a side wall that tapers outwardly from an upper to a lower peripheral edge. The shield is positioned within the central opening of the adapter such that the lower peripheral edge of the shield abuts the second cylindrical extent of the adapter. In this orientation, the locking apertures of the upper shield and adapter can be aligned.
The assembly further includes a target collimator. The collimator is defined by a diameter and an apertured peripheral edge. The peripheral edge is positioned adjacent the lower peripheral edge of the upper shield such that the apertures of the collimator are aligned with the threaded apertures of the upper shield.
A lower shield component is also included. This lower shield component is defined by an upper opening of a first diameter and a lower opening of a second reduced diameter. The lower opening functions in receiving a wafer pedestal. The upper opening has a flanged peripheral edge with apertures formed therein. The lower shield is positioned adjacent the peripheral edge of the target collimator, such that the apertures of the collimator are aligned with the apertures of the lower shield.
Finally, a series of threaded fasteners are secured within the apertures of the lower shield, the apertures of the collimator and the threaded apertures of the upper shield. This series of fasteners serves to secure, as a unit, the collimator and the upper and lower shields. Likewise, a pair of locking fasteners are removably secured within the locking apertures of the upper shield and adapter. These locking fasteners permit the collimator, the upper shield, and the lower shield to be removed from the adapter as a unit. In this regard, the first diameter of the lower shield and the diameter of the collimator are smaller than the diameter of the second cylindrical extent of the adapter, thereby permitting removal of the shield assembly from the upper peripheral edge of the adapter.
The foregoing has outlined rather broadly the more pertinent and important features of the present invention in order that the detailed description of the invention that follows may be better understood so that the present contribution to the art can be more fully appreciated. Additional features of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.